[[ sneck ]]
Try reading again. :) I knew the guy, personally. His masters thesis was on the subject of optimizing lightbulb construction. I actually read the whole thing -- before submission, in fact, as he wanted my editorial help, and knew I could also follow the math.
The gathered experimental data fit a simple 11th order curve (with an error under 5 parts in 10,000), over a range of more than three orders of magnitude, in bulb life. i.e., of the form ax^11+k, no other elements.
Actually, it does, when you're justifying running some lighting circuits off a (slight :) step-down auto-transformer. Accurate predictions of results _do_ lead to repeat business. :)
No I don't. For many kinds of environments there is a _minimum_ recommended level of illumination for the task(s) done there. (more below)
For standard incandescent bulbs, going up 'one standard wattage' results in about 50% more light output. Note; at the _same_ service life, light output _does_ correlate linearly with power consumption. One gets 50% more light from a 75 watt bulb, vs a 60 watt one, because of design differences that result in a 25% _lower_ life expectancy for the 75 watt bulb.
_That_ depends on the environment, and the situation. In business settings you have to have certain minimums to keep OSHA inspectors, insurers, etc. happy. With built-in fixtures, you can't change the source to work- surface distance, so all you _can_ play with is the light output of the bulb. 'Subjective' perception, or not, that circa 50% range between adjacent standard bulb ratings _is_ enough that the 'legal' requirement can preclude using the next lower standard rating, but still allow the use of a, say, de-rated 130V bulb.
If they're regular bulbs, in flush-mount ceiling fixtures, there is a 'grabber' pole that makes that height pretty much a non-issue.
Now a _cord-supported_ can hanging 30+ ft above the nearest floor surface (and 6-8 ft below the ceiling) is an entirely different story. Can't use the grabber pole -- the fixture isn't 'stable' enough to grab the bulb, Have to bring in the portable man lift, move furniture out of the way for _that_, etc. it can easily take an hour or more, all told, to change a =single= light bulb. (One can probably, however, change at least 5-6 bulbs in the same room in 90 minutes total. :)